Pressurizing buildings to improve drying

ABSTRACT

A method of drying a building includes closing all openings in the building such that air movement out of the building is restricted, drawing air from outside the building, heating the outside air, and directing a stream of the heated outside air into the building through an input duct. The building air pressure of air inside the building is measured and compared to a desired building air pressure that is less than the input pressure. Where the measured building air pressure is greater than the desired building air pressure, a substantially controlled flow of air is allowed to exit the building at an exhaust location and the flow of air from the building is controlled to maintain the building air pressure at the desired air pressure.

This application is a continuation-in-part (CIP) of U.S. patentapplication Ser. No. 10/751,455 “METHOD AND APPARATUS FOR CONTROLLINGHUMIDITY AND MOLD”, filed Jan. 6, 2004, the disclosure of which ishereby incorporated herein by reference.

This invention is in the field of drying building interiors that haveexcessive moisture accumulated therein, and in particular with dryingbuilding interiors with a pressurized flow of dry air.

BACKGROUND

It is well known that excessive moisture in buildings causesconsiderable problems. Drywall and flooring absorb moisture and arereadily damaged if the excessive moisture condition persists for anylength of time. Interior elements such as insulation, studs, and joistscan eventually be affected as well. Furthermore, mold begins to form onthe damp building materials, and can remain in the structure even afterit has dried, causing breathing problems for persons occupying thebuilding.

At the extreme, such excessive moisture conditions are exemplified by aflooded building. U.S. Pat. No. 6,457,258 to Cressy et al., “DryingAssembly and Method of Drying for a Flooded Enclosed Space”, disclosesan apparatus for drying flooded buildings that overcomes problems in theprior art. Such prior art is said to require stripping wall and floorcoverings and using portable dryers to circulate air to dry out theexposed floor boards, joists and studs. The methods were slow andallowed mold to form on the interior framing, which could then gounnoticed and be covered up and then later present a health hazard tooccupants.

The solution proposed by Cressy is to introduce very hot and dry airinto the building, indicated as being at 125° F. and 5% relativehumidity, in order to dry the building very quickly to prevent moldgrowth and allow an early return to occupants. In the apparatus ofCressy et al., outside air is heated by a furnace and the dry heated airis blown through a dry air duct into a location in the building. Aninput end of an exhaust duct is positioned in another part of thebuilding such that the dry air moves out of the dry air duct, picks upmoisture from the building and then moves into the input end of theexhaust vent and out of the building. In Cressy the warmer exhaust airis directed through a heat exchanger such that heat therefrom istransferred to the cooler outside air prior to heating by the furnace,thereby increasing the efficiency of the system.

Prior art systems for drying flooded buildings also include desiccantdehumidifiers that use a desiccant material with a high affinity towater to absorb water from the air, and refrigerant dehumidifiers thatcondense water out of the air by cooling it. In both of these systems,the water must be disposed of in some manner. The water absorbed by thedesiccant material is removed by subsequently drying the material. Thewater condensed by the refrigerant system is collected in a reservoirthat must be emptied from time to time or piped to a disposal area. Suchsystems are relatively costly to manufacture and operate, and arerelatively slow to remove moisture from the subject building.

U.S. Pat. No. 6,647,639 to Storrer, “Moisture Removal System”, addressesthe problem of extracting water from interior portions of a structuresuch as inside walls and from hardwood floors. Storrer discloses using ablower to blow (or draw) dry air through a hose and manifolds that canbe directed through injectors into the interior of walls.

Similarly, U.S. Pat. Nos. 5,960,556 to Jansen, “Method for DryingSheathing in Structures”, is directed to drying walls with warm, lowhumidity air. U.S. Pat. Nos. 5,893,216 to Smith et al., U.S. Pat. No.5,555,643 to Guasch, and U.S. Pat. No. 5,408,759 to Bass disclosesystems for drying walls by directing pressurized air into the inside ofthe wall.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system for dryingbuildings that overcomes problems in the prior art.

Co-pending United States Patent Application 2005/0145109 of the presentinventors Dancy et al. discloses a controlled system for maintaining adesired humidity level in buildings and for drying buildings. Portableheat exchanger units comprise a temperature adjusting element,illustrated for example as comprising a fluid coil and a fan drawing airfrom an inlet through the coil and out an outlet. The coil is connectedby conduits to a fluid heater or fluid cooler such that the air passingthrough the coil can be either heated or cooled. By drawing in outsideair and heating it, the relative humidity of the air is reduced, and thedrier air is directed into the building. A vent is provided, typicallysomewhere opposite the intake, so that the drier air moves through thebuilding and picks up moisture from building and carries it out throughthe vents.

The relative humidity of the air is an indicator of how much water theair is holding, and thus how much more water it can hold. The amount ofwater air can hold increases with the temperature of the air, and therelative humidity thus decreases as the temperature increases. By way ofillustration, in a closed room with standing water on the floor, therelative humidity of the air in the room would approach 100% (i.e. theair would become saturated with water) and so no more water wouldevaporate off the floor. Raising the air temp 10° C. will reduce therelative humidity by 50% to a 50% relative humidity, resulting in amoisture gradient between the water and the air, and thus more waterwill evaporate off the floor and the relative humidity will again riseto 100%, provided no air moves in or out of the room.

By bringing in a dry air stream at a first location in the room andopening an exhaust vent, such as a window, door, at a second location inthe room, air entering at the first location pushes the air in the roomtoward the second location and out the vent. As the dry air movesthrough the room it picks up moisture and takes the moisture out throughthe vent. Over time the water will eventually evaporate and be carriedout of the room.

A heat controller can be operated to supply heat at the proper rate toachieve a desired relative humidity in the air stream, and thus in theenclosed space. On a wet day for example if the outside air has arelative humidity of 100%, raising the temperature of the outside air by20° C. will reduce the relative humidity of the air stream to 25%.Alternatively raising the temperature of the outside air by 40° C. willreduce the relative humidity of the air stream to about 6% and providefast drying in a flooded building, where damage to sensitive materialsis not an issue.

The present invention provides, in a first embodiment, a method ofdrying a building. The method comprises closing substantially allopenings in the building such that air movement out of the building isrestricted; drawing air from outside the building, heating the outsideair, and directing a stream of the heated outside air into the buildingthrough at least one input duct at an input pressure; measuring abuilding air pressure of air inside the building; comparing the measuredbuilding air pressure to a desired building air pressure that is lessthan the input pressure; and where the measured building air pressure isgreater than the desired building air pressure, allowing a substantiallycontrolled flow of air to exit the building at an exhaust location andcontrolling the flow of air from the building to maintain the buildingair pressure substantially at the desired air pressure.

A significant proportion of buildings that require drying due to floodsor mishaps will be fairly poorly sealed against the elements. Forexample in many areas, especially those in warmer climates, vaporbarriers are not commonly installed. Thus it is possible to pressurizethe interior of these buildings with heated dry air using a fan similarto a furnace fan, or like available fan, to a level of about 0.2 to 0.5water column inches (″WC) and force air through the walls and ceilingsof the building. The method also provides improved drying of buildingsthat are better sealed against air movement.

For example, a portable heat exchanger unit comprising a fluid coilconnected to a fluid heater and a fan drawing air from an inlet throughthe coil and out an outlet can be used to draw in outside air, heat itto reduce the relative humidity thereof, and direct a stream of the dryheated outside air into the building through an input duct at an inputpressure of about 0.6-0.7″ WC. With all openings in the building closed,such as windows, doors, vents, or the like, air movement out of thebuilding is restricted to the extent possible. When the air stream isdirected into the closed building, the building air pressure inside thebuilding will rise. As the building air pressure rises, air inside thebuilding will seek to flow to the lower pressure ambient air outside thebuilding, and will thus flow out through cracks and the like in thewalls and ceiling. The dry air picks up moisture from inside thebuilding, and from inside wall areas to a certain extent as well, andcarries it out as it exits the building.

The input pressure developed by the fan is a pressure differentialbetween the air exiting the input duct and the ambient outside air.Where the doors and windows of the building are open a very low pressurewill develop in most buildings, depending on the number and location ofthe doors and windows. The fan will thus be drawing air in and blowingit out against negligible pressure. The volume of air in the air streamfor any given fan at those conditions will be known, and the fluidheater can be adjusted to provide the desired temperature rise to thatvolume of air flow.

When drying a building by directing a heated and dried air streamthrough the building the amount of time air remains in the building willdepend on the volume of the interior of the building. For example wherethe air stream has a volume of 5000 cubic feet of air entering thebuilding every minute (cfm), and the building has a volume of 25,000cubic feet, the air inside the building will essentially change everyfive minutes. At this rate of air movement, the amount of moisturecarried out by the air stream will depend on the degree of moisture inthe building, and the relative humidity of the entering air stream. Thelower the relative humidity of the air stream, the higher the moisturegradient between the air inside the building and the wet buildingsurfaces, and the faster moisture will be absorbed by the air. When theair is in the building, it absorbs moisture and the relative humiditythereof rises. The longer the air remains in the building then, the moremoisture it will absorb, and thus the longer the air remains in thebuilding, the lower the rate of moisture absorption and drying.

Basically then, for any given relative humidity of the air stream, thefaster the air moves through the building the faster the building willbe dried. The operator thus is typically attempting to push the airthrough the building as quickly as possible, and thus opens such windowsand doors as are available in order to reduce the pressure inside thebuilding to a minimum and maximize the volume of the air stream flowingthrough the building.

With the method of the present invention however, the operator willdetermine that at a building air pressure of 0.25″ WC, where the insidepressure will be such that the air will try to force its way throughwall openings, the fan will only create an air stream volume of perhaps3500 cfm instead of the 5000 cfm available where building air pressureis negligible. The operator then will start the fan with all buildingopenings closed. As the air stream enters the building, the building airpressure will rise, and the operator will monitor the building airpressure with a manometer or the like, with a view to attaining thedesired building air pressure of 0.25″ WC, and input air volume of 3500cfm.

With the doors, windows, and whatever other openings might be presentclosed, the building air pressure will rise to an equilibrium pointwhere the amount of air in the air stream will equal the amount of airleaking out of the building through door seals, window seals, cracks andthe like. Where the building is poorly sealed, the building air pressureat this equilibrium point may be less than the desired building airpressure of 0.25″ WC. In this situation the operator may choose tosimply allow the air to flow through the building at whatever thebuilding air pressure is at equilibrium, and then adjust the heat toraise the temp of the air stream to the desired level. Where obviouslarge air leakage is occurring the operator may attempt to seal theseleaks.

Alternatively the operator may increase the volume of air flowing intothe building by adding a second fan to boost air flow through the coil,or by adding a second portable heat exchanger unit, or by like meanssuch that the building air pressure rises above the desired pressure of0.25″ WC.

Where the building is relatively well sealed, the building air pressurewill rise, and could approach the input pressure developed by the fan.At that state very little air would be moving into the building.

In any event, when the building air pressure exceeds the desiredpressure of, in the present example, 0.25″ WC, the operator allows asubstantially controlled flow of air to exit the building at an exhaustlocation and controls the flow of air from the building to maintain thedesired air pressure. Typically the operator will accomplish this end bypartially opening a door or window in the building at a locationopposite the input location where the air stream is entering thebuilding.

The operator will adjust the heat supplied by the fluid heater to asetting where the fluid coil will raise the temperature of the airstream by the desired amount.

The invention further provides the opportunity to control the directionof the flow of air through the building by positioning the exhaustlocation. For example where one room or area is wetter than the rest ofthe building the exhaust location can be positioned such that the wetterarea is between the input location and the exhaust location. Air flowwill be greatest between the input and output location as the air streamseeks to exit the building to the lower pressure outside. Interior fanswill typically be provided at locations throughout the building toagitate the air and circulate same along the walls to improve drying,however by moving the air stream directly through the wetter areas ofthe building, drying times will typically be reduced. Where there aretwo wetter areas in a building, two exhaust locations could be providedto split the air flow and direct a portion of the air flow through eachwetter area. Similarly where a plurality of air streams are available,the input locations could be positioned to direct the air flow asdesired as well.

It is also contemplated that pressurizing the building interior willimprove the circulation of air through the building by pushing air intoall corners and like areas that are somewhat removed from the main airflow path. It is also contemplated that the pressurized air will alsopush against the wet surfaces improving moisture transfer from thesurfaces to the air.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof,preferred embodiments are provided in the accompanying detaileddescription which may be best understood in conjunction with theaccompanying diagrams where like parts in each of the several diagramsare labeled with like numbers, and where:

FIG. 1 is a schematic top view of a building interior showing allopenings in the building closed such that the building air pressurerises and at least some air exits the building interior through thebuilding structure;

FIG. 2 is a schematic top view of the building interior of FIG. 1showing a window opened to allow a controlled flow of air to exit thebuilding interior;

FIG. 3 is a schematic top view of the building interior of FIG. 1showing a window and a door opened to allow a controlled flow of air toexit the building interior through two locations; and

FIG. 4 is a schematic top view of the building interior of FIG. 1showing a window and a door opened to allow a controlled flow of air toexit the building interior through two locations, and showing anincreased amount of air being drawn into the building interior.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:

FIGS. 1-4 schematically illustrate a method of drying an interior 1 of abuilding 3. The method comprises closing substantially all openings inthe building, such as windows 5 and doors 7, such that air movement outof the building is restricted, as illustrated in FIG. 1. Outside air isdrawn from outside the building 1 and heated, and a stream 9 of theheated outside air is directed into the building 1 through an input duct11 at an input pressure.

While it is contemplated that other apparatuses could be used, in theillustrated embodiment, the air stream 9 is conveniently provided by aportable heat exchanger unit 13 comprising a fan and a coil heatingelement. The air is heated by hot fluid circulating through the coilfrom a boiler 15, or like fluid heater. As the air stream is forced intothe building through the input duct 17 at the input pressure developedby the fan, the air pressure in the building interior 1 rises, since thewindows 5 and doors 7 a have been closed. The input duct 17 issubstantially sealed to the building 3 to prevent escape of air. Using amanometer or like instrument, the building air pressure of the airinside the building 3 is measured, and compared to a desired buildingair pressure that is less than the input pressure. Typically the inputpressure will be about 0.6-0.7″ WC compared to the air pressure outsidethe building 3, and the desired building air pressure in the interior 1of the building 3 will be about 0.25-0.40″ WC, creating a pressuregradient between the building interior 1 and the air outside of thebuilding 3 such that air inside the building will seek to pass throughthe structure to the lower pressure outside the building.

At least some air will flow through cracks or the like in the walls androof, especially in buildings with no vapor barrier, as indicated byarrows 9A showing portions of the air stream 9 passing through the wallsof the building 3. For example, air will enter a crack in the interiorwall surface, and flow along the inside of the wall until it comes to acrack or the like in the outside wall surface through which the air willflow to the lower pressure outside. In this way, some air circulationwill be developed inside the walls that will help to dry the inside ofthe wall.

Typically in a relatively sound building after the fan has been runningfor a period of time and equilibrium has been reached, the measuredbuilding air pressure will be greater than the desired building airpressure. The operator will then select an exhaust location, typicallyan available window 5 or door 7, although an exhaust could be providedof any kind, and a substantially controlled flow of air will be allowedto exit the building at the exhaust location to maintain the desired airpressure. Typically the exhaust will be opened a small amount, and whenequilibrium is reached the building air pressure will be measured again.If it is still above the desired pressure, the exhaust will be openedfurther, and this process will be repeated until the desired buildingair pressure is attained, at which time the exhaust will be fixed inplace, the amount of heat supplied to the air stream will be adjusted toprovide the desired temperature rise, and drying will proceed. FIG. 2illustrates the window 5A being used to provide the exhaust.

The method of the invention also provides for directing the flow of theair stream 9 through the building such that the air flow is increasedthrough wetter areas or other desired areas of the building interior 1by configuring the input location of the input duct 17 and the exhaustlocation such that an air flow is created from the input locationthrough a desired area of the building to the exhaust location. Forexample FIG. 2 illustrates a desirable configuration of the input duct17 and exhaust location at window 5A where it is desired to increaseairflow through the room 19 in the building interior 1, such as wherethe room 19 may be wetter than the rest of the building interior 3. Thusa portion of the air stream 9A will continue to exit through thestructure, and a portion 9B will exit through the window 5A. Whilecirculation fans, not shown, will typically be used in the buildinginterior 1 to circulate air in the building against the walls, air flowthrough the room 19 will be greater than through the balance of thebuilding interior 1.

FIG. 3 illustrates a configuration where a substantially controlled flowof air is allowed to exit the building interior 1 at two exhaustlocations, the window 5A and door 7A, such that in addition to the airflow 9A through the structure, a first air flow 9B is created from theinput duct 17 through a first desired area of the building, the room 19,to the first exhaust location at window 5A, and a second air flow 9C iscreated from the input duct 17 through a second desired area 21 of thebuilding to the second exhaust location at door 7A. With the door 7Aopened, the window 5A will be closed somewhat compared to its positionin FIG. 2, since it will be desired to maintain about the same area ofopening that was provided by the window 5A alone in FIG. 2 using thewindow 5A and the door 7A in FIG. 3.

Where the building interior 3 is about equally wet throughout, theconfiguration of FIG. 3 allows the room 19 to experience sufficient airflow for drying that may not be available without an exhaust location inthe room 19.

In some less well sealed buildings, such as older or damaged buildings,the air stream provided by a single portable heat exchanger unit may notbe sufficient to raise the building air pressure to the desired levelbecause is leaking out as fast as it is coming in. It may be that theoperator will choose to simply let the air flow out of the buildingthrough the structure, or he could draw an increased volume of outsideair into the building interior 1 by adding a second portable heatexchanger unit 13A as illustrated in FIG. 4 directing a second airstream 9′ into the building interior through a second input duct 17A.The steps set out above would typically be followed to maintain thedesired building air pressure.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

1. A method of drying an interior of a building, the method comprising:closing substantially all openings in the building such that airmovement out of the building is restricted; drawing outside air fromoutside the building, heating the outside air, and directing a stream ofthe heated outside air into the building through at least one input ductat an input pressure; measuring a building air pressure of air insidethe building; comparing the measured building air pressure to a desiredbuilding air pressure that is less than the input pressure; and wherethe measured building air pressure is greater than the desired buildingair pressure, allowing a substantially controlled flow of air to exitthe building at an exhaust location and controlling the flow of air fromthe building to maintain the building air pressure substantially at thedesired air pressure.
 2. The method of claim 1 further comprising, wherethe measured building air pressure is less than the desired building airpressure, drawing an increased volume of outside air into the building.3. The method of claim 2 further comprising increasing the amount of airdrawn into the building until the desired building air pressure issubstantially maintained.
 4. The method of claim 1 comprisingconfiguring an input location of the at least one input duct and theexhaust location such that an air flow is created from the inputlocation through a desired area of the building to the exhaust location.5. The method of claim 4 comprising allowing a substantially controlledflow of air to exit the building at first and second exhaust locationsconfigured such that a first air flow is created from the input locationthrough a first desired area of the building to the first exhaustlocation and such that a second air flow is created from the inputlocation through a second desired area of the building to the secondexhaust location.
 6. The method of claim 1 comprising directing a streamof the heated outside air into the building through a plurality of inputducts located at a plurality of input locations.
 7. The method of claim1 wherein the desired building air pressure is between 0.25″ WC and0.70″ WC compared to an ambient pressure of the outside air.
 8. Themethod of claim 1 wherein the outside air is heated with a heatingelement, and wherein the amount of heat supplied to the air stream isadjusted.